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Infimum Limit


The infimum limit, also called the limit inferior or lower limit, of a sequence of real numbers a_n, written liminf and pronounced 'lim-inf,' is the limit of

 A_n=inf_(k>=n)a_k

as n->infty. Note that by definition, A_n is nondecreasing and therefore has a limit in the affinely extended real numbers. For example, suppose a_n=(-1)^n/n, then for n odd, A_n=-1/n, and for n even, A_n=-1/(n+1). Another example is a_n=sinn, in which case A_n is a constant sequence A_n=-1.

When limsupa_n=liminfa_n and the common value is finite, the sequence converges to the real number

 lima_n=limsupa_n=liminfa_n.

Otherwise, the sequence does not converge.


See also

Infimum, Limit, Lower Limit, Supremum

Portions of this entry contributed by Todd Rowland

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Cite this as:

Weisstein, Eric W., with contributions by Todd Rowland. "Infimum Limit." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/InfimumLimit.html

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